1. The Field of the Invention
This invention relates to semiconductor processing technology and, more particularly, to novel systems and methods for sealing joints, conduits, pumps, and heaters carrying ultra-pure fluids for processing operations.
2. The Background Art
Chemically clean environments maintained for handling pure de-ionized (DI) water, acids, chemicals, and the like, must be maintained free from contamination. Leakage into or out of a liquid must be eliminated. Moreover, leaching and chemical reaction between any contained fluid and the carrying conduits must be eliminated.
In particular, the semiconductor manufacturing industry relies on numerous processes. Many of these processes require transportation and heating of DI water, acids and other chemicals. Whereas other industries may require purities on the order of parts per million of contaminants, the semiconductor industry may require purities on the order of parts per trillion.
Several difficulties exist in current systems for heating, pumping, and carrying process fluids (e.g. acids, DI water, etc.). By clean or ultra-pure is meant that gases or liquids cannot enter or leave a conduit system to produce contaminants above permissible levels. To obtain and maintain a clean conduit system, traps are to be avoided. Traps may be small passageways, nooks, crannies, threads, or dead ends, where chemicals may break down over time to form contaminants. Likewise, particulate matter may accumulate in such traps.
Currently, a system is needed that is both durable and responsive for heating process fluids. For example, many immersion heaters exist in the prior art. Immersion heaters place a heating element, typically sheathed in a coating, directly into the process fluid. The heating element and process fluid are then contained within a conduit. A failure of a sheath may directly result in metallic or other contamination of the process fluid.
Contamination in a process fluid may destroy tens of thousands of dollars in value by introducing contaminants into a process. Temperature transients in immersion heaters may overheat a sheath. Temperature transients in radiant heaters may fracture a rigid conduit.
Material transitions between parts fitted together and made of the same material, and of parts fitted together and made from different materials are of substantial interest. Monolithic parts (e.g. long sections of continuous tubing) may be formed of a suitable material. However, fittings to connect other fluid couplings to such a monolithic part may create traps, introduce new materials, create problems in sealing, perpetuate leaks, or the like.
It is desired to provide heating without an immersion-heating element. It is also of interest to provide trap-free, leak-free, non-reactive, reliable, durable, and consistent transitions between ultra-pure, non-reactive parts, whether of the same or of different materials. In particular, it is desired to form a fluorocarbon part transitioning to another fluorocarbon part with a stable seal. Also desired is transition of a quartz, particularly a fused quartz, conduit transition to a fluorocarbon part.
Fluorocarbons have a substantial amount of creep or inelasticity inherent in their mechanical properties.
Elevated temperatures are required in semiconductor processing. Temperatures over 100.degree. C., especially those sustainable over 120.degree. C. may be required. In certain instances, temperatures as high as 180.degree. C. may be approached. Thus, it is desired to provide a chemically clean, particle-free, fully flushable, leak-free system for pumping, heating, carrying, and otherwise handling ultra-pure fluids at elevated temperatures. Durable seals having minimum of maintenance, reduced or eliminated maintenance while maintaining a clean, non-reacting environment, are needed. It is preferred that all heating, pumping, and carrying of process fluids include virtually no possibility of contact with any metals regardless of the ostensibly non-reactive natures of such metals, regardless of a catastrophic failure of any element of a transfer or conduit system.